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Enzymatic Degradation of Starch—Usage of β‐Cyclodextrin for Inactivation of Pullulanase

Ulbrich, Marco; Bültena, Matthias; Flöter, Eckhard

The cyclic oligosaccharide β-cyclodextrin (β-CDx) is investigated regarding its ability on principle to reduce the debranching activity of pullulanase (PUL) or even terminate the enzymatic hydrolysis process of starch polymers completely. For this purpose, dissolved β-CDx (aqueous solution) is mixed with the diluted PUL compound (solution) and conditioned (stirred at 40 °C for various durations [0, 20, 40, and 60 min; at 26.75 nmol β-CDx U−1] and at various β-CDx dosages [5.35, 13.375, 26.75, and 53.5 nmol β-CDx U−1; reaction time 60 min]). The PUL-CDx-mixtures are subsequently added to a 2.5% w/w starch solution (related to the initial specific debranching activity; 1593.6 NPUN g−1/557.8 U g−1) and gently stirred for 20 min at 40 °C before final thermal inactivation. The obtained samples are diluted and characterized molecularly, i.e., by means of size exclusion chromatography (SEC). An increasing β-CDx dosage reduces the degree of molecular degradation systematically reflecting a successively reduced enzyme activity. However, the reaction time (PUL-CDx-mixture) has no impact on the enzyme's activity since the starch degradation is marginally and the SEC-chromatograms similar to the one of the initial starch. Restrictions of the enzyme inhibiting effect of β-CDx are found terminating the hydrolysis process in a starch suspension.
Published in: Starch - Stärke, 10.1002/star.202300163, Wiley